Classification of Matter
How do atoms combine to make
different types of matter?
Why
?
Look at the things in this room. They are all matter. That matter may
be pure or it may be a mixture. Can you tell by looking at it? What if
you looked at it under a microscope? Then could you tell? Something
that looks pure may not really be pure. It depends on what type of
particles an object or substance is made of. In this activity we will
explore how the smallest chemical units of matter determine whether
something is classified as an element, a compound, or a mixture.
Model 1 — Atoms, Particles, and Molecules
T & RSq & R
R
?
atom
8
partic
les
?
molecule
?
chemi
cal
bond
RSq
molec
ule
ato
ms
5 particles
TSq2R
chemi
cal
bond
Sq2
molec
ule
SqR3 & TSq
chemical
bond
Classification
of Matter
1
5 particles
2
POGIL™ Activities for High
School Chemistry
1. Locate the circled molecule of RSq in Model 1.
a. Find a second RSq molecule and circle it.
b. How many atoms are in a molecule of RSq?
2. Find and circle a molecule of TSq2R in Model 1.
a. How many different types of atoms are found in a molecule of
TSq2R?
b. How many Sq atoms are in a molecule of TSq2R?
3. Locate the drawing labeled SqR3 & TSq in Model 1.
a. How many different types of atoms are found in the sample of
SqR3 & TSq?
b. How many different types of molecules are found in the sample
of SqR3 & TSq?
4. When two atoms are touching in the drawings of Model 1, what
is holding the atoms together?
5. As a group, discuss the following questions and record your
answers:
a. Can a particle be a single atom?
b. Can a particle be a molecule?
c. How many particles are in the drawing representing T & RSq & R
in Model 1?
d. What is your group’s definition of the word “particle” as it is
used in chemistry?
6. Compare the codes listed at the top of each drawing in Model 1
with the shapes in that box.
a. What do the letters R, Sq, and T in the codes represent?
b. What do the small numbers (subscripts) in the codes represent?
c. When atoms are touching, how is that communicated in the
code?
Classification
of Matter
3
d. What is the common characteristic of the samples in which an
ampersand (&) is used?
e. In Model 1 there are three drawings that are labeled with a
question mark. Write codes to properly label these
drawings.
4
POGIL™ Activities for High
School Chemistry
7. Appoint one group member to cut apart Model 1 to separate the
nine drawings. As a team, sort the drawings into two groups—
one group where all the particles in the drawing are identical,
and a second group in which the drawings contain more than
one type of particle.
Read This!
Matter is classified as a pure substance when all of the particles are
identical. Matter is classified as a
mixture if there are different types of particles present.
8. Identify which drawings from Question 7 are pure substances
and which are mixtures. List the codes for the drawings in the
appropriate places below.
Pure Substances
Mixtures
9. How are the codes (chemical formulas) for pure substances
different from those for mixtures?
10. As a team, take the set of pure substances drawings from
Question 8 and sort them into two new groups, those
containing only one type of atom and those with two or
more types of atoms.
Read This!
Elements are defined as pure substances made from only one type of
atom. Compounds are defined as pure substances made from two or more
types of atoms.
11. Identify which drawings from Question 10 are elements and
which are compounds. List the codes for the drawings in the
appropriate places below.
Elements
Compounds
12. How are the codes (chemical formulas) for elements different
from those for compounds?
Classification
of Matter
5
13. Use what you have just learned about chemical formulas to
identify each of the following as an element, a compound or
a mixture.
a. Br2
b. NaHCO3
c. C6H12O6 &
H2O
d. Cu & Zn
6
e. CO2
f. Al
POGIL™ Activities for High
School Chemistry
14. Explain the difference between:
a. An atom and an element.
b. A molecule and a compound.
Classification
of Matter
7
Extension Questions
15. It is often useful to separate matter. Physical methods of
separation (filtering, distillation) do not require a chemical
change. In other words, no chemical bonds are broken or
formed during the separation. Chemical methods of separation
(decomposition, electrolysis) require a chemical change. In
other words, chemical bonds are broken and/or formed
during the separation.
a. Is straining cooked pasta from water a physical or chemical
separation?
b. Is using a fuel cell to separate water into hydrogen and
oxygen a physical or chemical separation?
c. Which type(s) of matter (mixtures/compounds/elements)
could be separated by physical methods?
d. Which type(s) of matter (mixtures/compounds/elements)
would need to be separated by chemical methods?
16. Students in a chemistry course were asked the following
question on a unit exam: “Draw a dia- gram representing an
element using circles as atoms.”
a. The following diagrams represent two typical answers
given by students. Which drawing is the best representation
of an element? Explain.
Drawing A
Drawing B
b. Imagine that the atom in Drawing B had been removed by
physical separation from one of the substances in Model 1.
What substances could have been the source of the atom
in Drawing B?
8
POGIL™ Activities for High
School Chemistry